The Terror of Sleep Paralysis Explained

An abduction scene from the movie ‘The Fourth Kind’

You wake from what feels like a deep sleep, opening your eyes to a darkened room.  It looks like your bedroom, sort of, but there’s something…

You can’t move!  It feels like there’s something, someone holding you down.  Your senses jump into overdrive, and you scan the room, as best you can.  Is there someone there?  Angels?  Aliens?  Demons?  You’re sure you can see creatures moving around you, and you can definitely feel that someone or something has invaded your home.

Are you having a supernatural experience?  Is this the start of an alien abduction scene?  Have you been targeted by malevolent forces intent on doing you harm?  A great many people believe the answer is yes.  And who can really say that one person’s experience is to be believed, while another’s is not?

The above scenario is actually a fairly common experience.  Some sources suggest that as many as 6-40% of the world population has or will experience, either once or multiple times, something like that described above (with a good deal of variation in the details).  That isn’t, however, a description of an abduction event or a supernatural encounter.  It’s a description of a sleep paralysis event.

Sleep paralysis is, as you might already be aware, a neuro-physiological problem that a great many people suffer through.  It is terrifying, it is violating, and it is apparently unavoidable (for some people).  Sleep paralysis is characterised as an interruption to the REM sleep cycle within the transition between wakefulness and rest, wherein the subject suffers from atonia, which renders them immobile for a period ranging from several seconds to several minutes, and possibly up to an hour.  During which time the person experiences elements from their dreams in what feels like their conscious world.

In truth, we all experience atonia while we sleep, which is, in simple terms, the brain’s mechanism for stopping you from acting out your dreams in real time.  Atonia means muscle weakness, and in relation to REM sleep, it means complete autonomous muscle immobility.  Dreams occur most often during the sleep cycle called REM or rapid eye movement, and each night when we enter dreamland, our brains undergo a change which stops our skeletal motoneurons from responding to signals to move as may be generated by dream content.

Le Cauchemar (The Nightmare), by Eugène Thivier (1894)

The neurophysiology of this process is well understood, to a point, but the finer details are hotly argued among neuroscientists.  It is believed that a condition known as IPSP or inhibitory postsynaptic potential – which is triggered by glycinergic inhibition of motoneurons, and makes postsynaptic neurons less likely to generate an action potential – is the main mechanism that causes atonia during REM sleep.[1]  In simpler terms, a chemical in the brain interrupts communication between certain synapses, thereby stopping them from reacting to dream-induced signals.  Other theories suggest that there may be other neurotransmitters involved, but the basic process is as described.

This system of synapses and neuronal potentials is complicated, in case you couldn’t tell from the above.  As a result, there are several things that can go wrong (in addition to sleep paralysis):

  • Narcolepsy – the brain’s inability to regulate sleep-wake cycles, often resulting in disrupted nocturnal sleep patterns and sudden onset of sleep during the day.
  • Cataplexy – the rare neurological condition causing involuntary and sudden loss of muscle tone or strength while fully conscious.
  • RBD or rapid eye movement behaviour disorder – the malfunction of the atonia process resulting in a person moving or physically acting out dreams while sleeping (sleepwalking is a type of RBD).

So, basically, sleepy paralysis is the opposite of RBD.  Instead of acting out the dream, the person experiences dream states during the transition between sleep and wakefulness, while still unable to move.  It doesn’t take a great deal of imagination to understand how that could be a very disturbing and traumatic experience.  Consider also that some people experience the phenomenon several times a night for weeks at a time, and it becomes clear that research into possible treatments is sorely lacking at the moment.

The Nightmare, by Henry Fuseli (1781) is thought to be one of the classic depictions of sleep paralysis perceived as a demonic visitation.

It’s believed that certain lifestyle situations contribute to an increased susceptibility for sleep paralysis (or any of the atonia related maladies listed above).  Those range from stress, to excessive use of stimulants, to the use of some medications, such as those used to treat ADHD.  Some doctors suggest that one who suffers through these illnesses can mitigate their risk of further events by strictly regulating sleep schedules, using good sleep hygiene, and avoiding the supine position (on your back, facing up), but there is no known method to cure or entirely stop the events from happening.

Now that we know what it is, we can discuss what it means.

If you experienced what was described at the opening of this post, would you think yourself crazy?  Would you believe that you had experienced the strangeness that was your dream being played out before your open eyes, or would you defer to what, in your experience, was a completely real event?  Certainly no one would blame you if you did.  Well, few would.

In his 2012 book The Magic of Reality, Richard Dawkins, the world famous militant-atheist and avowed skeptic, suggested that all reported alien abductions are examples of mental illness, with the lead culprit being sleep paralysis.  This book was targeted at the Young Adult audience and apparently was meant as a primer to the natural sciences.  It’s informative, but dismissive.

Dawkins’ attitude toward the phenomenon of alien abduction and other paranormal experiences is prevalent in skeptical circles, and justifiably so.  When one considers the almost archetypal scenes and characters associated with sleep paralysis events, one must admit that a great many people who report those experiences as real events, are simply mistaking what amounts to a dream for an actual experience.  Sleep paralysis is historically given as the standard explanation for alien abductions, as mentioned, and for angelic, demonic and all manner of other supernatural experiences.  The legendary succubus/incubus experience is thought to be the quintessential sleep paralysis motif, and it’s difficult to deny the connection.

Is that the end of the story though?  Not at all.

Sleep paralysis is currently the best explanation we have for many of these experiences, in spite of the adamant stance of those who wish to validate the abduction storyline.  Occam’s Razor tells us that the sleep paralysis or “mental illness” explanation is preferable over the fanciful stories of abduction and molestation, but Occam didn’t mean for us to reject all other theories over the simplest, he tells us simply to favour the simplest.

Is it possible that some people are being visited in their sleep by unknown entities?  The answer can only be yes.  Is it possible that some people are really experiencing nightmarish events at the hands of something otherworldly?  Again, the answer can only be yes.  In turn though, is it possible that most are being tricked by their senses and a malfunctioning system meant to protect us from ourselves?  Yes, that’s also possible.

The point of all this is simply to say that no one has all the answers.  Certainty is the sign of a small mind, and “…as for me, I know only that I know nothing”.


[1] Patricia L. Brooks, John H. Peever. Identification of the Transmitter and Receptor Mechanisms Responsible for REM Sleep Paralysis. The Journal of Neuroscience, 18 July 2012, 32(29): 9785-9795

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